An increasing number of consumers believe foods that are free of synthetic or chemical additives are healthier. In response to these consumer trends and preferences, the food industry has focused efforts on offering various alternatives such as clean label and/or natural products that are free from artificial preservatives while retaining similar microbial safety characteristics as compared to conventionally prepared products.
Curing agents such as salts of sodium nitrate and sodium nitrite (“cured”) have a long history of preserving the microbial safety of processed meat formulations as they provide functional benefits of antimicrobial and antioxidant activities in addition to delivering desirable color and flavor attributes characteristic of such products (See e.g. Pegg, R. B., and F. Shahidi. 2000. Nitrite curing of meat: the N-nitrosamine problem and nitrite alternatives. Food & Nutrition Press, Inc., Trumbull, Conn., incorporated by reference herein in its entirety).
However, the consumption of processed meats formulated with such curing agents has recently been linked with an increased risk of colorectal cancer due to the formation of cancer causing N-nitroso compounds and poly cyclic aromatic hydrocarbons (See e.g. Santarelli, R. L., Pierre, F., & Corpet, D. E. 2008. Processed meat and colorectal cancer: a review of epidemiologic and experimental evidence. Nutrition and Cancer, 60(2), 131-144., incorporated by reference herein in its entirety). Moreover, the International Agency for Research on Cancer (IARC, a subsidiary of WHO) and American Institute of Cancer Research (AICR) recently classified processed meats as Group 1 carcinogenic agents to humans (See e.g. Bouvard, et al. 2015, on behalf of the International Agency for Research on Cancer Monograph Working Group, The Carcinogenicity of consumption of red and processed meat. The Lancet Oncology. Published Online: 26 Oct. 2015., incorporated by reference herein in its entirety).
Meat products prepared without a curing agents either from synthetic or naturally occurring sources (“uncured” or “nitrate or nitrite free”) are more susceptible to the growth of pathogens due to their antimicrobial nature. Listeria monocytogenes and Clostridium species are two pathogens that are of particular concern in “uncured” or “nitrate or nitrite-free” products. Listeria monocytogenes is a psychrotroph that can grow even at refrigeration temperatures and thus pose food safety risk in extended shelf life ready to eat (RTE) meat and poultry products. Spore forming enterotoxigenic species of Clostridia such as Clostridium botulinum and Clostridium perfringens associated with processed meat and poultry are also of particular concern. While the heat applied in manufacturing RTE processed meat products is sufficient to inhibit vegetative cells, spores will not be inactivated but rather may germinate and develop into vegetative cells.
Spoilage organisms also play an important role in reducing the shelf-life of both raw (fresh) and uncured RTE refrigerated meat and poultry. For example, species of Pseudomonas and Lactobacillus are predominantly responsible for undesirable defects such as off-flavors, discoloration, gas and slime etc.
Additionally, in recent times there has been a movement to reduce the sodium content in food (See e.g. Scientific Report of the 2015 Dietary Guidelines Advisory Committee. Advisory Report of the Secretary of Health and Human Services and the Secretary of the Agriculture). Sodium is an effective preservative and its reduction makes formulations more vulnerable to a higher risk of pathogen and spoilage growth and thus results in shorter product shelf life (See e.g. Desmond, E. 2006. Reducing salt: A challenge for the meat industry, Meat Science, 74 (2006), pp. 188-196, incorporated by reference herein in its entirety).
In cured products, low levels of sodium nitrite, approx. 50 ppm, are sufficient for the inhibition of Clostridium species in processed meat formulations (See e.g. Hustad, G. O., J. G. Cerveny, H. Trenk, R. H. Deibel, D. A. Kautter, T. Fazio, R. W. Johnston, and O. E. Kolari. 1973. Effect of sodium nitrite and sodium nitrate on botulinal toxin production and nitrosamine formation in wieners. Appl. Microbiol. 26:22-26. incorporated by reference herein in its entirety).
Nevertheless, the maximum allowed level of 156 ppm sodium nitrite when used without the addition of adjunct antimicrobials is insufficient for the inhibition of Listeria monocytogenes (See e.g. Farber, J. M., R. C. McKellar, and W. H. Ross. 1995. Modelling the effects of various parameters on the growth of Listeria monocytogenes on liver pate. Food Microbiol. 12:447-453., incorporated by reference herein in its entirety).
Similar or comparable results are expected in inhibition of Listeria and Clostridia sps. when alternative sources of nitrate or nitrite (derived either by synthetic or fermentation methods) used to deliver similar concentrations equivalent to sodium nitrite as described in the examples listed above.
Previous studies have investigated organic acids or their salts for the inhibition of these pathogens in RTE processed meat applications. In particular, studies suggest that acetic acid or its salt alone when used at concentrations (<1%) that are expected to provide acceptable sensory attributes in RTE meat and poultry products, failed to inhibit C. perfringens in turkey breast meat (See e.g. Juneja, V. K., and H. Thippareddi. 2004. Inhibitory effects of organic acid salts on growth of Clostridium perfringens from spore inocula during chilling of marinated ground turkey breast. Int. J. Food Microbiol. 93:155-163., incorporated by reference herein in its entirety).
Additional studies demonstrated that 0.3-0.5% sodium diacetate when used alone or in combination with additional antimicrobials were effective in controlling Listeria monocytogenes in turkey slurries formulated with and without sodium nitrite (See e.g. Schlyter, J. H., Glass, K. A., Loeffelholz, J., Degnan, A. J., Luchansky, J. B., 1993. The effects of diacetate with nitrite, lactate, or pediocin on the viability of Listeria monocytogenes in turkey slurries. Int. J. Food Microbiol. 19, 271-281., incorporated by reference herein in its entirety). However, the suggested levels were higher than the maximum allowed levels (0.25% of the product formulation; FSIS 7120 list) in meat and poultry products in the U.S. and is expected to contribute an unacceptable flavor to the finished product. Additionally, other attempts have demonstrated the use of propionic acid or its salt in combination with pediocin to control Listeria monocytogenes. Nevertheless, to date known methods have failed to address control of Clostridia species, one of the predominant pathogen risks in uncured meat and poultry products.
While it is known to utilize nisin in combination with organic acids, the efficacy of these systems required emulsifiers and were dependent on the sequential addition of these individual components. In addition, these compositions did not demonstrated efficacy to inhibit pathogens and spoilage of concern under the conditions specified herein that represent uncured, high moisture and low-sodium processed meats (See e.g. U.S. Patent Application Publication no. 2013/0012428 A1 to Jacobus et al.; incorporated by reference herein in its entirety).
U.S. Pat. No. 6,509,050 B1 to Henson et al., which is incorporated by reference herein in its entirety, demonstrated the use of polyphosphates in combination with an organic acid or its salts in controlling Listeria monocytogenes in a broth model and spoilage microorganisms in a cured meat system. As is known in the art, phosphates are typically used in meat applications to retain moisture and to improve the yield. However, there was no evidence of the efficacy of this approach for the inhibition of pathogens in a low sodium uncured meat system. Moreover, the levels of phosphates described therein are higher than currently allowed in the U.S. (0.5%; FSIS 7120 list).
To date, the simultaneous inhibition of Listeria and Clostridia species in RTE refrigerated meats formulated without sodium nitrite has not been reported. It is desirable to have a method that can demonstrate efficacy against foodborne pathogens and spoilage microorganisms in an “uncured” or “nitrite-free” systems with acceptable flavor that are high in moisture (65-80% by weight), low in salt (<2% by weight), and in a pH range of 5.5-8.5.
Therefore, the cumulative effects of replacing chemical preservatives with clean label options in addition to lowering the sodium levels in foods has obligated food manufacturers to compromise shelf life. Particularly, at risk are food products with high moisture and low sodium which favors microbial growth such as the uncured meat application provided above. While there are several ways (methods and antimicrobials) to control the foodborne pathogens and spoilage in traditional processed meat and poultry products formulated using sodium nitrite, there is a need in the art for methods to eliminate such compromise and enhance the safety of clean label products formulated without sodium nitrite (uncured or sodium nitrite-free). It is also preferred to demonstrate a method of inhibiting the pathogens and spoilage with one solution that has broad antimicrobial properties in diverse matrices and applications.
The current invention provides such a method of inhibition. These and other advantages of the invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.